Phase shifter



Aug; 12'; 1952 Filed June 2, 1950 M. DENIS ErAL 2,607,031

PHASE SHIFTER 2 SHEETS-SHEET 1 M. DENIS ET PHASE SHIFTER Filed June 2,1950 2 SHEETSSHEET 2 2/75/1701:: ecfl. DEA/AS psmee filzug i I I iiIIIPIIiII n M. w

Patented Aug. 12, 1952 .rnasn'srnr rnn I j iMarc'el Denis tan'd -:PierrePalluel, Paris, France,

assignorswto Gompagnie G-enerale de Teler-gr-aphie Sans Fil, acorporation of France Application June 1950, serial No. 165,802

f "In-Fiance June 20, 1949 2 Claims. 1

.This invention relates 'nltra short "Wave oscillators and providescertain Improvements a phase shifter for an ultra shortwave oscillatorwhich comprises a "travel-- liirrg waver-valve with an side reactionchannel between its output and itsinpm and which is characterised inthatthe said channel con-- tains a filter designed to select a possibleoscillation range on a-sin'gle mode and a phase shifter :foradjusting-the phase so as 'to render this-oscillation possible. Morespecifically the invention provides improved phase shifters formedulating orcontro'lling the frequency of such an oscillator.

According to this inventionthe phase shifter to phase shifters foremployed comprises a dielectric substance subi jected to an electricfield and the required variation of phase is achieved by variation ofthe dielectric constant of this substance by regulating or varying saidelectric field.

The invention is based on the fact that certain substances such as earthal'kaline titanate in the. crystalline state or agglomerated by aceramic process, in pure condition or in mixed combinations of variableproportions, exhibit a nal on the field generating means, variation oftuning or modulation of the frequency of the oscillator may be effected.

The invention is illustrated in and further explained in connection withthe accompanying drawings in which:

Figure 1 shows diagrammatically an installation embodying the invention,and

Figures 2 and 3, which show two alternative constructions for the phaseshifter.

Referring to Figure 1, which is a purely diagrammatic representation ofthe oscillator as a whole, T is a travelling wave tube of which theinput and output are coupled by a reaction channel G containing a filterF and a phase shifter D. Modulation from a source M controls the phaseshift introduced by the phase shifter D, and the modulated energy passesvia a filter F into the load circuit through a coupling C.

Figure 2 shows one form which, in accordance with the present inventionthe phase shifter D line comprising an external conductor! and internalconductor-2, thespace between these two conductors being filledwith adielectric material '3 of the nature already mentioned herein.

The dimensions, of the section A must boa-small enough to ensure that noparasitic mode will be propagated therein. The sections 31 and B2 aretransition section's constituted by .co-axial lines each a quarter of awave long at; the "mean operating frequency and of the sametransversedimensions as section A. These sections are filled with adielectric material whose constant is the geometric mean between that ofthe material 3 and that of'space. Two :c0 ;-axial :line sections Cl and(32 of progressively, increasing section serve to adapt thedimensionsofthe co-axialline sections BI and B2 to those of the parts DI and D2 ofthe reaction channe'Lu In thisarrangement the modulating voltage isapplied to the terminals of the condenser which is constituted by theconductors l and 2 of the assembly of co-axial line sections. Ifrequired a D. crvoltage may be superposed upon the modulating voltage soas to regulate the mean dielectric constant "of ;.the substance-3 to asuitable value.- If lis the-length of the section A and 27 is the phasevelocity the total phase shiftco isrgiven for a mean value E0 of thedielectric constant'is'givenaby: I I

where F is the frequency.

If under the influence or the modulation voltage, Eo varies by M3, thevariation Ac of phase is given by:

T t an (A where A is the wave length.

For example if A28 cm., and E0=l00 we have d1+d2 0.5 cm. Supposing wemay take d1=1 mm. and (12:3 mm.

equal respectively to The characteristic impedance of this co-axial lineis:

= 138 log (lg/d VEO In this way the elements of the system may becompletely determined in design and the data Z g7 ohms.

necessary for calculating impedance adaptation obtained. 1

Figure 3 shows an example of phase shift construction adapted to thecase where the reaction channel is made up of rectangular guides. Only asection taken parallel to the electric field is shown the sectionparallel to the magnetic field being of the same appearance except forthe dimensions.

The phase shifter is here constituted by a block 5 of dielectricmaterial placed in a restriction G3 of rectangular section insertedbetween the guide parts GI, G2 of the reaction channel.

Perpendicular dimensions of the section of the block area and brespectively. 1

- Impedancea'dapting or transition sections of 4 We claim: 1. Agenerating circuit for ultra high frequency waves comprising atravelling wave tube having an input and an output, a feed-back channelcoupling the output of the said tube to the input for causing thetube tooperate as an oscillator, a phaseshifter and a filter, said phaseshifter being dimensioned so as to introduce a phase displacementcompleting the phase displacement along the said feedback channel, up tosuch a value that the total retrocoupled energy phase displacementbetween said output and input sustains oscillations in said tubecircuit, and said filter being dimensioned so as to select a band ofprogressively varying cross section are interposed at G4 and'GS. "Theguide section which is filled with dielectric material will exhibit thesame characteristic impedance as the guideiparts GI and G2 ifthecorresponding dimensions :are

I guides 8 and 9; so as to provide a condenser to which the modulationvoltage is applied by means of leads l0 and II passingthrough aperturesin the guide G3; These current leads" do not cause high frequencydisturbances because energy is not propagated between G3 and 5. i

The invention is not restricted to the particular examples described andillustrated.

predetermined width in the spectrum of said oscillations, said phaseshifter comprising a body of dielectric material whose dielectricconstant depends upon the electric field to which it is subjected, saidbody being arranged to be traversed by the high frequency wave generatedby the said generating circuit, a pair of electrodes arranged onopposite sides of said body, and means for applying between saidelectrodes a voltage which sets up anelectric field across the saidbody, thereby causing the said voltage to vary the phase velocity ofthewavetraversing the said body, and then to vary the said phasedisplacement introduced by the said phase shifter.

2 .v A generating circuit for ultra high frequency waves according toclaim 1, in which said means for applying a voltage between said pair ofelectrodes comprises a source of alternating modulating voltage formodulating the generated ultra high frequency oscillations.

' MARCEL DENIS.

PIERRE PALLUEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,421,725 Stewart June 3, 19472,473,556 Wiley June 21, 1949 2,483,818 Evans Oct. 4, 1949 2,521,760Starr Sept. 12, 1950

